This invention relates to filter cigarettes. More particularly, the present invention relates to filter cigarettes which are adjustable by the smoker to vary the air dilution value.
It is known to produce variable dilution cigarettes having integral rotatable elements for controlling dilution. The rotatable element can be a rotatable band of tipping paper retained by stationary bands against axial displacement and having a slit overlying a slit in the filter plug wrap with which it can be rotated into and out of registry. Alternatively, it can be a rotatable section of the filter plug, carrying with it a section of tipping paper extending over a stationary section of the filter plug. The extending section of the tipping paper has a slit which overlies a slit in the plug wrap on the stationary filter plug segment. The slits can be moved in and out of registry by rotating the rotatable filter segment. Such a cigarette is described in commonly-assigned U.S. Pat. No. 4,532,943, which is hereby incorporated by reference in its entirety.
In the manufacture of these types of cigarettes, the slits in the tipping paper and plug wrap are most easily formed by simultaneously slitting both layers with a knife or laser beam. The cigarettes are therefore assembled initially with the slits fully in registry both longitudinally and rotationally. The dilution level can then be adjusted by rotating the rotatable segment varying the rotational registry of the slits.
In such a cigarette, it is intended that the longitudinal registry of the slits not change as the filter segments are rotated. However, with certain constructions, rotation of the rotatable segment may cause longitudinal motion of the rotatable segment, affecting the longitudinal registry of the slits and impairing control of the dilution level.
It would be desirable to be able to provide a variable dilution cigarette of the type described above in which a change in the longitudinal registry of the slits does not affect control of the variable dilution feature.